The present invention relates to an improvement of a sound source device for a portable apparatus having a sound emitting part whose frequency domain is limited.
In general, a sound source device included in an electronic instrument or the like converts artificial sounds generated on the basis of rectangular waves, sawtooth waves and sinusoidal waves or those recording and editing natural sounds, instrumental sounds or the like to a digital quantity with an A-D converter or the like and performs waveform generation with previously set waveform data, while a speaker or the like having an excellent sounding band is connected to a reproduction system in this case.
On the other hand, a sound emitting part of a speaker or the like provided on a portable apparatus such as a portable telephone is designed miniature, lightweight and thin in order to make the best use of portability characterizing the portable apparatus. Therefore, an efficient frequency domain in its frequency characteristics becomes a limited one and is not suitable for reproduction of music requiring a wide frequency domain, while it operates at a low voltage of about 3 V as to its internal operating pressure and hence sound pressure is also low.
In the portable apparatus such as a portable telephone, as hereinabove described, only a sound emitting part whose efficient frequency domain is limited can be used due to restriction in structure, a sufficient sound emitting quantity cannot be obtained, and musical expression has also been limited.
The present invention has been proposed in order to solve the aforementioned problems, and aims at providing a sound source device, in which a sufficient sound emitting quantity can be attained also in a portable apparatus such as a potable telephone, capable of obtaining reproduced sounds of musically rich expression.
A first mode of the sound source device according to the present invention is a sound source device comprising a waveform table having previously generated waveform data and a waveform reading part reading the said waveform data from the said waveform table at an arbitrary reading interval for reading the said waveform data at a prescribed interval on the basis of externally supplied music performance information and outputting the same from a sound emitting part as a reproduced sound, in which the said waveform data is a pseudo-rectangular wave obtained by eliminating a harmonic component exceeding a prescribed order from a rectangular wave.
According to the first aspect of inventive the sound source device, the pseudo-rectangular wave obtained by eliminating the harmonic component exceeding the prescribed order from the rectangular wave is such that the top portion of the wave has a corrugated shape where a plurality of irregularities having different heights continue, whereby, also when part of the top portion reaches the maximum range of an amplifier in formation of a chord, for example, the overall top portion is prevented from being cut and the reproduced sound is prevented from occurrence of a feeling of unfitness. As to the aforementioned pseudo-rectangular wave, further, it follows that leading and trailing edges a pulse have inclinations, whereby generation of folding noise resulting from abrupt swinging of the waveform in the time-base direction, the so-called jitter, can be suppressed and audibility can be improved. In addition, it eliminates the harmonic component exceeding the prescribed order, i.e., eliminates a high-order harmonic component, whereby the harmonic component is prevented from exerting influence on a peripheral device and the overall system can be stably operated.
A second aspect of the sound source device according to the present invention is such that the said eliminated harmonic component is a harmonic component having a frequency exceeding a prescribed frequency domain in at least the frequency characteristics of the said sound emitting part.
According to the second aspect of the inventive sound source device, it eliminates a harmonic component of a frequency at least exceeding the prescribed frequency domain in the frequency characteristics of the sound emitting part, whereby a high-order harmonic component can be eliminated and a reproduced sound matching with sound emitting characteristics of the sound emitting part can be obtained when setting a domain of the sound emitting part having excellent sound emitting efficiency as the prescribed frequency domain, for example.
A third aspect of the sound source device according to the present invention is such that the said pseudo-rectangular wave has such spectral density that spectral density in a prescribed frequency domain in the frequency characteristics of the said sound emitting part in the case of Fourier-transforming the pseudo-rectangular wave is higher than a rectangular wave having a pulse duty factor of 50%.
According to the third aspect of the inventive sound source device, the spectral density of the pseudo-rectangular wave becomes higher than the rectangular wave having the pulse duty factor of 50%, whereby a reproduced sound obtained with this pseudo-rectangular wave improves in energy density, improve becomes an excellent reproduced sound.
A fourth aspect of the sound source device according to the present invention is such that the said pseudo-rectangular wave is such that the spectral quantity of spectral lines excluding at least a reference spectral line among spectral lines in the said prescribed frequency domain in the case of Fourier-transforming the said pseudo-rectangular wave is at a value obtained by multiplying the spectral quantity at a corresponding frequency by a prescribed coefficient in a continuous spectrum in the case of Fourier-transforming an isolated rectangular wave.
According to the fourth aspect of the inventive sound source device, the spectral quantity of the pseudo-rectangular wave becomes large, whereby a reproduced sound obtained with this pseudo-rectangular wave not only improves in energy density and improves in sound emitting efficiency but also a sound emitting quantity rises and a more excellent reproduced sound can be obtained.
A fifth aspect of the sound source device according to the present invention is a sound source device comprising a waveform table having previously generated waveform data and a waveform reading part reading the said waveform data from the said waveform table at an arbitrary reading interval for reading the said waveform data at a prescribed interval on the basis of externally supplied music performance information and outputting the same from a sound emitting part as a reproduced sound, in which the said waveform data is such a pseudo-rectangular wave that the top potion of the wave has a corrugated shape where irregularities continue and leading and trailing edges of the waveform have inclinations.
According to the fifth aspect of the inventive sound source device, the top portion of the wave has a corrugated shape where a plurality of irregularities continue, whereby, also when part of the top portion reaches the maximum range of an amplifier in formation of a chord, for example, the overall top portion is prevented from being cut and the reproduced sound is prevented from occurrence of a feeling of unfitness. Further, the leading and trailing edges of a pulse have inclinations, whereby generation of folding noise resulting from abrupt swinging of the waveform in the time-base direction, the so-called jitter, can be suppressed and audibility can be improved.
A sixth aspect of the sound source device according to the present invention is such that the said pseudo-rectangular wave is such that the pulse widths of two pulse waves included in one cycle are different from each other.
According to the sixth aspect of the inventive sound source device, the spectral density of such a pseudo-rectangular wave that the pulse widths of two pulse waves included in one cycle are different from each other becomes higher than a rectangular wave having a pulse duty factor of 50%, whereby a reproduced sound obtained with this pseudo-rectangular wave improves in energy density, improves in sound emitting efficiency and becomes an excellent reproduced sound.
A seventh aspect of the sound source device according to the present invention is such that the said pseudo-rectangular wave is such that heights of the said irregularities include different heights.
According to the seventh aspect of the inventive sound source device, the heights of the plurality of irregularities of the pseudo-rectangular wave are different from each other, whereby, even if a most projecting part of the top portion reaches the maximum range of an amplifier and is cut in formation of a chord, for example, the remaining parts are not cut, whereby the reproduced sound is prevented from occurrence of a feeling of unfitness.
An eighth aspect of the sound source device according to the present invention is such that the said waveform tables are plural and have waveform data of the same form respectively.
According to the eighth aspect of the inventive sound source device, the plurality of waveform tables have waveform data of the same form respectively, whereby it is possible to readily form a chord by reading the same while varying reading intervals in a waveform reading part and adding these, for example.
A ninth aspect of the sound source device according to the present invention is such that the said waveform tables are plural and have waveform data of different forms respectively.
According to the ninth aspect of the inventive sound source device, excellent reproduced sounds can be obtained with respect to various music performance information by so devising that each is having a pseudo-rectangular wave having high spectral density or a high spectral quantity in the prescribed frequency domain in the frequency characteristics of the sound emitting part also when the frequencies are different, for example, in the respective ones of the plurality of waveform tables thereby selecting a pseudo-rectangular wave of a proper frequency in correspondence to information from a music performance information source. Further, it also becomes possible to reproduce various instrumental sounds having different tone colors by inputting pseudo-rectangular waves of different timbre in the respective ones of the plurality of waveform tables.
A tenth aspect of the sound source device according to the present invention further comprises control means controlling an operation of reading the waveform data of the said plural waveform tables at various frequencies respectively and superposing the same and an operation of differently using the same individually in compliance with the said music performance information.
According to the tenth aspect of the inventive sound source device, excellent reproduced sounds can be obtained with respect to formation of a chord and various types of music performance information.
The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.